Constellation Md. Calvert Cliffs 1 reactor shut

NEW YORK, July 16 (Reuters) - Constellation Energy Group Inc's CEG.N 873-megawatt Unit 1 at the Calvert Cliffs nuclear power station in Maryland shut by early Thursday from full power early Wednesday, the U.S. Nuclear Regulatory Commission said in a report.

The 1,735 MW Calvert Cliffs station is located in Lusby in Calvert County, about 55 miles southeast of Washington. There are two units at the station, 873 MW Unit 1 and the 862 MW Unit 2, which entered service in 1975 and 1977.

The NRC renewed the plant's original 40-year operating licenses in 2000 for another 20 years until 2034 and 2036 - the first extensions granted to a commercial nuclear power plant.

Unit 2 continued to operate at full power.

One MW powers about 800 homes in Maryland.

In 2008, UniStar Nuclear Energy LLC, a venture between Constellation and France's Electricite de France SA (EDF) (EDF.PA), filed an application to build one of Areva SA's CEPFi.PA 1,600 MW Evolutionary Power Reactor (EPR) at the site.

The NRC will likely make a decision on the construction and operating license in 2011-2012 about 42 months after UniStar submitted the application.

Using an industry estimate of $4,000 per kilowatt, the new reactor could cost about $6.4 billion. Other nuclear operators considering the EPR, however, have estimated total costs as high as $10 billion.

Constellation, of Baltimore, owns and operates about 9,000 MW of generating capacity, markets energy commodities in North America, and transmits and distributes electricity to about 1.2 million customers and natural gas to 600,000 customers in Maryland. (Reporting by Scott DiSavino; Editing by John Picinich)